Electrical resistor



June 4, 1963 H. DOUNDOULAKIS ELECTRICAL RESISTOR 3 Sheets-Sheet 1 Filed Aug. 4, 1960 INVENTOR //4//-7S.D0z//VDOUL4/(/5 ATTORNEY J 1963 H. DOUNDOULAKIS ELECTRICAL RESISTOR 3 Sheets-Sheet 2 Filed Aug. 4, 1960 ATTO R N EY June 4, 1963 H. DOUNDOULAKIS 3, 2,

ELECTRICAL RESISTOR Filed Aug. 4, 1960 T1 IE.

5 Sheets-Sheet 5 all #5045 .Dowvp r/LAK/s 1 BY ATTORNEY l N E N T OR United States Patent 3,092,800 ELECTRICAL RESISTOR Helias Doundoulakis, Brooklyn, NY, assignor to Constantine A. Michalos, Fort Lee, NJ. Filed Aug. 4, 1960, Ser. No. 47,549 8 Claims. (Cl. 338-143) This invention relates to a method and apparatus for providing a device for movement about a helical path around a toroid, and relates more particularly to a mechanism and means for providing a variable or traveling device such as a contact for interweaving about a helical path around a toroid for electrical devices such as p0- tentiometers, autotransformers, variable resistors, variable inductors and tape recorders or such as a device for carrying a tool for cutting a helix circumferentially about a toroid.

In many applications it is important that given an applied electric potential between two points of an extended element, a second value of electric potential be accurately derived. This is done by applying a direct current or alternate current between two input contacts connected by the extended element, and removing the second value of electric potential by an output contact along the extended element. The two input contacts are usually fixed in position. The second electric potential is functionally dependent on the applied potential of the extended element and in addition it is dependent on the position of the output contact along the extended element.

In the use of the mechanism as a means for providing a traveling device such as a tool for cutting helical grooves about a toroid it is important to cut the grooves in an accurate predetermined mathematical pitch. The controlled pitch is necessary to produce a precisely cut groove in a form of a helix around a toroid that may be used for winding in the groove a wire or mandrel for use in todays complex commercial electronic instruments.

To better understand this invention it is important to keep in mind the following concepts and parameters:

In the case of rheostats and linear potentiometers the bility material so that a magnetic flux can find a free path to link the turns situatedbetween the output contacts. In the case of the potentiometers the mandrel consists of a low permeability dielectric or metal about which a fine wire is wound;

The mandrel may be arranged in different shapes. For example, it may be straight or curved. In the case of a straight mandrel the contact is usually driven by a worm drive for precision. In the curved case the mandrel usually takes the form of a circle or a helix while the cont-act is attached to a rotating shaft;

Total impedance is the impedance across the two input contacts. In the case of potentiometers the impedance is mainly resistive. The total impedance may be related to a desirable value to match the impedance of the potential source. It may have to be sufliciently high so that given a certain value of input potential the resulting current will not overheat and damage the device. Since the resistance of available wires is rather low to build up necessary high resistance values, very small wire diameter and long lengths of wires are employed. High resistance Potentiometers are also frequently needed to 3,002,800 Patented June 4, 1963 produce negligible loading to where they are attached, as in the case of more than one potentiometer operating in tandem. Since reducing the wire diameter also limits the allowable current through the extended element it is desirable that higher impedance be achieved by use of longer length of wire, rather than the use of smaller wire diameter.

Winding angle is the angle of shaft rotation required to move the sliding contact from one end of the extended element to its other end. A large angle value for this parameter is desirable. If the winding angle in gear driven electric device is large backlash gear errors become negligible. In addition it is easier to set a particular position corresponding to a proportional potential value with greater accuracy, if the winding angle is large.

Resolution refers to the smallest increment of potential that can be read as compared to the total input potential. This is proportional to the inverse of the number of turns around a mandrel. Therefore, the greater the number of turns the higher the resolution. If the winding angle is large and the wire diameter is large the sliding contact can contact only one turn and with less variable contact resistance. If a contact travels along the length of the wire, without jumping from turn to turn of the winding, the electric device will have a theoretically infinite resolution.

Linearity of a given potentiometer is the capacity of a potentiometer to produce a slider output voltage that is directly proportional to the angular rotation of the shaft driving the sliding contact compared to the winding angle. For a high degree of linearity the wire diameter must be uniform. That is, the resistance of each turn must be very close to the same value and the spacing between turns must be uniform. Here again, the longer the mandrel and the larger the wire diameter the higher will be the linearity. For example, an excursion of the wire diameter by 00005 of an inch will contribute less to the nonlinearity if the diameter of the Wire is 0.010 than if it were 0.002. In addition, if the accuracy by which each wire turn can be set with respect to the input terminal is constant, the resulting error will be less, if the winding angle is larger.

The aforementioned qualifications may be summarized in that a more accurate potentiometer or similar device can be produced it it is possible to employ a length of mandrel far in excess of those presently available.

Various mechanical devices have heretofore been developed for increasing the length of the mandrel but these solutions have not been found satisfactory. Helipots have been introduced in which the mandrel takes the form of a helix but commercially available helipots have about ten mandrel turns. Another approach lately employed was to attach the wire longitudinally on thin tape. The tape, which constituted the mandrel shifted between two spools in a manner similar to that used in the case of tape recorders. In this case the contacting brush is fixed while the wire on the tape slides with respect to the contact.

One of the disadvantages of the helipots and the tape type devices was that after the sliding contact reaches the end of travel along the extended element, the contact has to travel the entire length backwards before it can start from the beginning again. For most applications continuity is necessary, so that after the sliding contact travels through the extended element it can reach the beginning and can start all over again without reversal in the direction of travel of the contact.

It is the purpose of this invention to provide a path in the form of a helix around a toroid and means for traveling continuously about the helical path around the toroid.

An object of this invention to provide an electric device having an extended element wound circumferentially in a helix around a toroid.

Another object of this invention is to provide a mechanism for supporting and directing a movable device about a helical path around a toroid.

Another object of this invention is to provide an electric device having an output potential of theoretically infinite resolution.

A further object of this invention is to provide an electric device having a slider output potential of theoretically infinite resolution with an instantaneous variation of potential from maximum to minimum while the slider travels continuously in one direction.

Another object of this invention is to provide a tape recorder having a magnetic recording head continuously operating in one direction for continuously recording or playing back without necessitating the removal or reversal of the tape.

Another object of this invention is to provide a potentiometer device having a long winding angle with continuity of motion of the sliding output contact at a relatively small overall diameter by utilizing a sliding contact traveling around a helical toroidal path.

A further object of this invention is to provide a potentiometer with a long mandrel wound circumferentially in a helix around a toroid and having a variable cross section to obtain a predetermined variable output potential.

Another object of this invention is to provide in a potentiometer device a long length of extended resistance element in the case where infinite resolution is required by winding it around a helical toroidal configuration.

A further object of this invention is to provide a potentiometer having more than one extended element in tandem or in parallel wound circumferentially in a helix around a toroid to exceed a potential accuracy and size requirement available in a single element potentiometer.

An additional object of this invention is to provide a mechanism supporting a cutting tool traveling circumferentially in a helix around a toroid to cut a helical groove in the toroid in which an extended electric element may be wound.

Other objects and features of the invention will appear as the description of the particular physical embodiment selected to illustrate the invention progresses. In the accompanying drawings, which form a part of this specification, like characters of reference have been applied to corresponding parts throughout the several views which make up the drawings.

FIGURE 1 is a plan view of a mechanism in accordance with a preferred embodiment of the invention;

FIGURE 2 is a sectional view of the mechanism taken on line 2-2 of FIGURE 1;

FIGURE 3 is a side elevational view of the mechanism shown in FIGURE 1;

FIGURE 4 is a top view of an element of the mechanism of FIGURE 1;

FIGURE 5 is an end view of the element shown in FIGURE 4;

FIGURE 6 is a view of another element of the mechanism shown in FIGURE 1;

FIGURE 7 is a side elevational view of an assembly of the mechanism of FIGURE 1;

FIGURE 8 is a side elevational view of an element of the assembly of FIGURE 7;

FIGURE 9 is a sectional view taken on line 99 of FIGURE 8;

FIGURE 10 is a side elevational view of another element of the assembly shown in FIGURE 7;

FIGURE 11 is a sectional View taken of line 1111 of FIGURE 10;

FIGURE 12 is a side elevational View of still another element of the assembly shown in FIGURE 7;

FIGURE 13 is a sectional view taken on line 1313 of FIGURE 12;

FIGURE 14 is a plan view of an element shown in FIGURE 1;

FIGURE 15 is a fragmentary sectional view showing a method of assembling two elements of the mechanism shown in FIGURE 1;

FIGURE 16 is a fragmentary sectional view showing the installation of elements shown in FIGURE 15 within the mechanism taken on line 16-16 of FIGURE 1;

FIGURE 17 is an enlarged fragmentary sectional view of a portion of the sectional view shown in FIGURE 2;

FIGURE 18 is an enlarged fragmentary sectional view of the mechanism taken on line 18-18 of FIGURE 1 rotated degrees.

FIGURE 19 is a view of the mechanism as shown in FIGURE 18 showing a modification of the cylindrical ring assembly;

FIGURE 20 is a view of the mechanism as shown in FIGURE 18 showing another modification of the cylindrical ring assembly;

FIGURE 21 is a view as shown in FIGURE 16 showing a modification of the extended element; and

FIGURE 22 is a view as shown in FIGURE 16 showing another modification of the extended element.

In carrying the invention into eflect in the embodiment which has been selected for illustration in the accompanying drawings and for description in this specification and referring now particularly to FIGURES l to 5, a mechanism 1% such as a donut shaped solid or torus 1 is provided with a continuous helical groove 14 in which is positioned an extended element or wire 16 wound on a mandrel 18 as shown in FIGURES 15 and 16. The extended element need not be a wire 16 wound on a mandrel 18 but may be a single strand of wire 11 as shown in FIGURE 21 or two wires 12 and 13 as shown in FIGURE 22, coiled in the helical groove 14 around the toroid.

The toroid 1, as best shown in FIGURES 4 and 5, comprises a plurality of spherical balls 20, supported in hearing sockets 22 on the top and bottom sides of the torus 1 (see FIGURE 17) between the successive grooves of the helical groove 14-. Bearing grooves 23 are located in a pair of plates 24 and 26, see FIGURE 14, of a housing 28. The spherical balls 20 ride within grooves 23 supporting the torus 1 for free rotation between the plates 24 and 26.

Another groove 32, as best shown in FIGURE 1, is provided along the outermost part of the torus 1. Two slotted metallic slip rings 34 and 35 (see FIGURES 2, 5 and 6) separated by insulation 36 are inserted in the groove 32. Each of the slip rings 34 and 35 may be split in two halves for easy insertion around the groove 32. of the torus 1. An alternative method of assembly may be to have the torus 1 split in two halves at the groove 32 with full circular corrugated slip rings 34 and 35 positioned in the groove 32.

In this embodiment as shown in FIGURES 15 and 16 the mandrel 18 is shown with a rectangular cross-section. This is done to minimize the difference between outside diameter and inside diameter ratio of the mandrel loops to wind the wire 16 closer together and thus increase the number of loops of wire. The wire 16 is wound around the mandrel 18 before the mandrel 18 is bent and wound around in the grooves 14 of the torus 1. The mandrel 18 is completely wound around the torus 1 until its two ends meet and connect together. The ends of the wire 16 are then electrically connected, one end to the ring 34 and the other end after completing its travel around the torus is connected to the other ring 35.

Located on the side of the housing 28 are two contacts or brushes 38 and 39. The brush 38 is in sliding contact with the ring 34 and the other brush 39 is in sliding contact with the other ring 35. These contacts are connected to input terminals 40 and 41 across which is placed an input direct current or alternate current to 1 plates 24 and 26. A helical grooved cylinder 58, see

FIGURES l and ll, rotates freely within the bearings 52 and 53 around the spherical balls 20 traveling in the grooves 69. A gear 56, see FIGURES 12 and 13, is attached to the outside diameter of the cylinder 58 rotating within the bearings 52 and '53. The gear, in turn being driven by a motor M through gear 59. As cylinder rotates by means of gear 56, the spherical balls 20 travel with respect to the helical groove 60 and since the position of the cylinder is fixed laterally with respect to the plates 24 and 26 the torus 1 is forced to rotate, about its axis, the cylinder 58.

On the cylinder 58 is located a window 62 in which a cartridge 66 may carry an output contact or brush 67, see FIGURE 18. The brush 67 is electrically connected to slip ring 68 which in turn is connected to brush 70 to transfer output potential from its slip ring 68 to terminal 72 depending on the location of contact 67.

In place of the cartridge 66 may be located a bracket 74 on which may be attached a cutting tool 76 used in cutting the helical groove 14 about the torus 1 in accurate predetermined mathematical pitch, see FIGURE 19. The tool 76 may be fed radially inwardly to cut the groove as deep as desired.

The apparatus may be used as a tape recorder by wind ing a memory element 78 within the groove 14 and connecting the ends to form a complete helical torus. The cartridge 66 may then be replaced by a bracket 74 on which may be mounted a magnetic head 82 with a pick up element 84 to pick up or record electric signals as the well known magnetic memory devices. In this case the recorder may continuously operate in one direction for continuously recording or playing back without necessitating the removal or reversal of the tape.

The invention hereinabove described may therefore be varied in construction within the scope of the claims, for the particular device selected to illustrate the invention is but one of many possible embodiments of the same. The invention, therefore, is not to be restricted to the precise details of the structure shown and described.

What is claimed is:

1. A mechanism for providing a variable contact for electrical devices comprising a toroidal configuration member having a continuous helical groove circumferentially inscribed around its surface to form a continuous path, electric input and output terminals, an electric extended element curved in said helical groove and connected at its ends to said electric input terminals, a movable contact supported above said electric extended element and electrically connected to said output terminal and in sliding contact with said electric extended element, and means for movement of said contact around a circular path about the generating circle of said torus and for movement of said toroid about its axis, whereby said sliding contact moves in a helical course around the toroid in a continuous movement.

2. A mechanism as claimed in claim 1, said extended element including a plurality of parallel wires.

3. An apparatus comprising a torus having a continuous helical groove circumferentially inscribed around its surface at least one extended element Wound in said helical groove around said torus, at least one fixed electrical contact connected to said extended element and at least one sliding contact disposed for movement along the entire length of said extended element.

4. An apparatus as claimed in claim 3, said extended element comprises a mandrel, a metallic Wire wound around said mandrel, at least one sliding contact in electrical continuity with said mandrel, a revolving gap-less cylinder supporting said sliding contact and revolving said contact around said torus that the sliding contact is displaced from turn to turn of wire as the revolving cylinder and the torus revolve in predetermined speeds, a continuous slip ring surface provided circumferentially on said cylinder, a support operable to rotate about said cylinder and a brush mounted on said support and operable to rotate with said support around said cylinder whereby the contact between said slip ring surface and said brush remains at constant distance from said brush support.

5. A device comprising a toroid having a continuous helical groove around its core and a second groove circumferentially around its perimeter, a pair of slip rings insulated from said toroid and from each other extending around the second groove, circumferentially around the perimeter of said toroid, a housing extending around the perimeter of said toroid, a pair of spaced plates supported by said housing on each side of said toroid said plates providing an opening and circular grooves on their surfaces facing said toroid, a plurality of spherical balls supported for rotation in said grooves on each side of said toroid to support said toroid for rotation between said plates, a mandrel, a wire wound around said mandrel, said mandrel with said Wire bent and wound completely around within the helical groove of the core of said toroid until the ends of said mandrel meet and each of the ends of said wire connected to each of said slip rings after said Wire completely extends around the helical path of within the groove of said toroid, a pair of brushes, each in electrical sliding contact with each of said slip rings, extending from said housing, an input electric potential supplied across said brushes, cylinder interlocked around the core of said toroid and having an internal helical groove engaging said spherical balls for rotation within said grooves, a pair of bearings supporting said cylinder with the opening of said plates for rotating said cylinder around the core of said toroid, means for rotating said cylinder to drive said toroid through said spherical balls, and an output contact supported by said cylinder to pick up variable output potential as the cylinder rotates about the core of said toroid.

6. A device as claimed in claim 5 wherein said torus is constructed out of high permeability material, and said mandrel and wire replaced by a single strand of Wire.

7. A multi-turn potentiometer comprising a core in the form of a toroid, a pair of metallic slip rings encircling the outside periphery of said core, an extended element wound in a helical path around'said toroid and said slip rings, each of its ends connected to one of said slip rings, a potential impressed across said extended element through said slip rings, spherical balls supported within the upper and lower surface of said core, a pair of spaced plates defining circular grooves on the surface in which said spherical balls rotate and operate to support said core for rotation between said plates, a cylinder having an internal helical groove operable to rotate around said core, a brush supported on said cylinder electrically contacting said extended element as said cylinder rotates about said core, the groove of said cylinder contacting said spherical balls, and means to rotate said cylinder around said core to produce a transverse force on each of said spherical balls and thereby rotate said core through said spherical balls whereby a variable output potential is derived.

8. An apparatus comprising a torus having a continuous helical groove circumferentially inscribed around its surface to form a continuous path of several turns around said torus, a pair of spaced plates having parallel planes mounted on each side of said torus, circular grooves provided on the inner surface of said plates following the extremities of said torus, ball bearing interposed between said plates and the extremities of said torus for rotation of said torus between said plates, bearings supported between said plates transverse of the planes of said plates and encircling the generating circle of said torus, a cylinder having an internal helical groove being coaxially dis- 7 posed with and supported by said bearings, driving means operable to rotate said cylinder within said bearings whereby said cylinder groove is operable to exert side- Wise force on to said bearings to force the torus to rotate between said plates upon rotation of said cylinder by said driving means.

References Cited in the file of this patent UNITED STATES PATENTS 622,542 Moore Nov. 27, 1900 8 Tinus Apr. 13, 1954 Kagan et a1 Apr. 10, 1956 Roberts Mar. 12, 1957 Delmonte Sept. 24, 1957 Brown et al Oct. 22, 1957 Mansky et a1 Dec. 8, 1959 Falco May 31, 1960 

1. A MECHANISM FOR PROVIDING A VARIABLE CONTACT FOR ELECTRICAL DEVICES COMPRISING A TOROIDAL CONFIGURATION MEMBER HAVING A CONTINUOUS HELICAL GROOVE CIRCUMFERENTIALLY INSCRIBED AROUND ITS SURFACE TO FORM A CONTINUOUS PATH, ELECTRIC INPUT AND OUTPUT TERMINALS, AN ELECTRIC EXTENDED ELEMENT CURVED IN SAID HELICAL GROOVE AND CONNECTED AT ITS ENDS TO SAID ELECTRIC INPUT TERMINALS, A MOVABLE CONTACT SUPPORTED ABOVE SAID ELECTRIC EXTENDED ELEMENT AND ELECTRICALLY CONNECTED TO SAID OUTPUT TERMINAL AND IN SLIDING CONTACT WITH SAID ELECTRIC EXTENDED ELEMENT, AND MEANS FOR MOVEMENT OF SAID CONTACT AROUND A CIRCULAR PATH ABOUT THE GENERATING CIRCLE OF SAID TORUS AND FOR MOVEMENT OF SAID TOROID ABOUT ITS AXIS, WHEREBY 